Import sources from parent project

[Andrey via Digitalmars-d-learn]

Hi,
I have got this structure of my project:
parentapp
    dub.json
    source
        common.d
    childapp1
        dub.json
        source
            app.d
            somefile.d
    childapp2
        dub.json
        source
            app.d

The "childapp1" and "childapp2" are standanole subprograms. I 
want to import file "common.d" in both "app.d". How to do it 
correctly?

I tried to write "import common;" but got error: " Error: module 
`common` is in file 'common.d' which cannot be read".
In "parentapp/dub.json" I also added these lines:
"dependencies": {
    "parentapp:childapp1": "*",
    "parentapp:childapp2": "*"
},
"subPackages": [
    "./childapp1/",
    "./childapp2/"
]